Corrosion behaviour of magnesium/aluminium alloys in 3.5 wt.% NaCl

Corrosion behaviour of commercial magnesium/aluminium alloys (AZ31, AZ80 and AZ91D) was investigated by electrochemical and gravimetric tests in 3.5 wt.% NaCl at 25 degrees C. Corrosion products were analysed by scanning electron microscopy, energy dispersive X-ray analysis and low-angle X-ray diffraction. Corrosion damage was mainly caused by formation of a Mg(OH)(2) corrosion layer. AZ80 and AZ91D alloys revealed the highest corrosion resistance. The relatively fine beta-phase (Mg17Al12) network and the aluminium enrichment produced on the corroded surface were the key factors limiting progression of the corrosion attack. Preferential attack was located at the matrix/beta-phase and matrix/MnAl intermetallic compounds interfaces. (C) 2007 Elsevier Ltd. All rights reserved.